SODIS Roolz

Guest Post by Willis Eschenbach

One of the joys of writing for this blog is that I can promote good ideas. Here’s one I just came across, thanks to a commenter on another post of mine. The idea is solar disinfection of water, or SODIS. Follow the link, lots of good info.

Figure 1. The SODIS method in graphical form.

The idea is bozo simple. Put water into a clear plastic bottle. Shake it up well to oxygenate it. Put it out in the sun. Six hours in the sun and the oxygen plus the solar UV kills diarrhea.

I mean, how great is that? Now that’s solar tech I can get behind 100% … plus it uses up old water bottles. And doesn’t require any chemicals. Brilliant. Get the word out. Kids’ lives are at stake.

w.

86 thoughts on “SODIS Roolz

  1. No, no, no Willis…this is all wrong.

    1. You need a peer reviewed study to prove the method works.
    2. You need a deployment grant.
    3. You need supervisors and field techs.
    4. You need environmental impact studies.
    5. You need education and training in the field (after all these people can’t do this themselves).
    6. You need to have Greenpeace provide a permanent advisor for the village with a permanent stipend.
    7. You have to setup a recycling program for the bottles.

    Sheesh – what were you thinking? /sarc

  2. Dr A Burns says:
    May 15, 2011 at 2:45 pm
    Just how effective is it ? Is it equivalent to 5 minutes boiling for example ?
    “If they don’t have any bread, let them cake instead”.
    Boiling requires firewood [or dung] which is in short supply [and creates CO2 and ugly smoke, uhuh]

  3. Conclusion, throwing away our old water bottles is wastefull, we should save them and ship them to those who need them. It won’t even cost much to ship empty bottles.

    Personally I think that, after haveing spend billions of dollors over here to make clean, safe tap water, that bottled water is a scam (which show how really gullible people are today). Now, however, it turns out that the bottle is, in fact, usefull in and of itself. We should continue to make the bottles, just ship them to people who need them. We just don’t need to go to the time and expends of putting anything in them, or shipping them when they are full.

    And by scam, I personally like the bottled water labeled “Corpus Christy municipal water supply”, tap water, and they pay extra for this stuff! http://www.youtube.com/watch?v=XfPAjUvvnIc
    Finally, a USE for this scam!

  4. Dr A Burns says:
    May 15, 2011 at 2:45 pm
    Just how effective is it ? Is it equivalent to 5 minutes boiling for example ?
    —————————————————————————
    No, but. Follow the link and see http://pubs.acs.org/doi/abs/10.1021/es103328j

    Apparently, if done correctly it achieves a 75% reduction in infection. At zero cost of fuel, fuel being a major expense in those societies where the technique will be useful.
    Perfection is expensive. A vast improvement is cheap.
    Which is preferable?

  5. I’m sure some environmentalist will try to ban the procedure since it probably leaches a few parts per trillion of chemicals out of the plastic.

  6. Have we now accepted our global pre-industrial fate? Have you resigned yourself to slow, cold, and dim? Are we to be conditioned to accept this kind of 3rd world poverty even here by WUWT? I expected better from you. A man 30 years my senior, once offered some good advice many years ago: “Live as well as possible for as long as possible”. I intend to do so.

    This kind of abject minimalism does not offer much hope of a brighter future.

  7. What a great idea.
    In places with warmer/hot climates they have their ‘hot water’ tanks on their roofs.
    The sun heats that water up very well.

    We use the sun to our advantage as well.

    Small bungalow home. Have good windows all round, but specifically in dining area where they are numerous and facing east to SE, making a semi-circle wall of windows. The sun in winter heats this area of the house up to 27-28c (even if it’s -20c outside) as the sun shines in the windows directly up to 11:am or so, sometimes have to crack a window in the kitchen especially if the wood stove downstairs is still glowing. An air venting system carries this warm air all over the home. In summer not a problem, as the sun is higher so not directly in windows much past 8 am.

    I admire who ever designed and built this place.. even have a point system in the basement.
    How green is that? ;)
    Works too, as a broken hot water tank proved recently…

  8. Dennis Nikols said,
    That is truly simple and I have not doubt effective. However since few will make money on it I suspect less then well advertised.

    Two success stories, the first a for-profit.

    Mrs Djike lives with her family in the Song-Mahop slum in Cameroon. She has been selling chilled water to neighbours and travellers for many years. In 2008, a SODIS campaign was conducted in her neighbourhood. A promoter also visited her home and explained the use of the method. Mrs Djike hesitated at first. Considering the poor water quality in her slum, the method appeared to be too easy to work. After placing PET bottles on her roof and testing the method herself, she became an active user of SODIS method. Since then, her family is drinking clean water and suffers far less from diarrhoeal diseases.

    After her positive experience with the method, she also decided to offer her customers chilled SODIS water. The good quality of her water got around quickly in the neighbourhood. Today, she proudly says: “With the SODIS method, I already treat more than 40 bottles of water every day, which I chill and sell the next day. Thanks to the good water quality, I have acquired many new customers”. Since Mrs Djike also shows her customers how to use the SODIS method at home, she makes a significant contribution towards improving the living conditions in her neighbourhood.

    http://www.sodis.ch/index_EN

    In the beginning of the project we focused on the training of the households in the slums of Yaoundé, the capital city of Cameroun. Since 2009 we are working together with the medical faculty of the University of Yaoundé and have expanded our activities on other regions.

    In the slums of Yaoundé the method is already well anchored. More than 50,000 people are using it daily to treat their drinking water.

    http://www.sodis.ch/projekte/afrika/kamerun/index_EN

    According to the World Health Organization, more than two million people per year die of water-borne diseases, and one billion people lack access to a source of improved drinking water. (Wikipedia)

  9. Uhh… I wouldn’t assume this is a good idea over the long term, and yeah, some studies might be in order. Although letting plastic bottles filled with water bake out in the sun for ours may be effective at decontaminating the water, you’re also introducing unintended consequences, namely creating ‘plastic tea’ through the release of numerous petrochemical compounds from the plastic that leach into the water much more readily under high temperatures. BPA is one example, with several others to be concerned about depending on the grade of plastic. Yes, in a life or death situation such concerns are foolish, however for long-term, practical solutions in developing countries, there are much healthier and humane ways of decontaminating drinking water than scorching it in plastic. Here is just one example: http://www.enviro-stewards.com/?page_id=155

  10. I work with a Haitian doctor who routinely returns to the island to treat people and bring supplies. I told him about this as well to easily get good drinking water. It is a fantastic idea!

  11. I forgot. It also helps to try and filter the water through some cloth to get the large solids that make it cloudy. Cloudy water does not disinfect nearly as well and will get you sick.

  12. I like the idea, but I’d still favor a cap full of Clorox/quart. I don’t have the effectiveness numbers handy, but is sufficed for the U.S. Army while I was in, so probably quite a bit more effective than the SODIS method, but I agree, you can’t beat the cost. If this is the only method available, it sure beats nothing.

  13. Kyle Anders said, Although letting plastic bottles filled with water bake out in the sun for ours may be effective at decontaminating the water, you’re also introducing unintended consequences, namely creating ‘plastic tea’ through the release of numerous petrochemical compounds from the plastic that leach into the water much more readily under high temperatures.

    There has been some concern over the question whether plastic drinking containers can release chemicals or toxic components into water, a process possibly accelerated by heat. The Swiss Federal Laboratories for Materials Testing and Research have examined the diffusion of adipates and phthalates (DEHA and DEHP) from new and reused PET-bottles in the water during solar exposure. The levels of concentrations found in the water after a solar exposure of 17 hours in 60°C water were far below WHO guidelines for drinking water and in the same magnitude as the concentrations of phthalate and adipate generally found in high quality tap water.

    Concerns about the general use of PET-bottles were also expressed after a report published by researchers from the University of Heidelberg on antimony being released from PET-bottles for soft drinks and mineral water stored over several months in supermarkets. However, the antimony concentrations found in the bottles are orders of magnitude below WHO and national guidelines for antimony concentrations in drinking water. Furthermore, SODIS water is not stored over such extended periods in the bottles.

    http://en.wikipedia.org/wiki/Solar_water_disinfection

  14. Do the bottles need to be green in color (like ginger ale’s), or clear, like carbonated water’s? Carbonated —? Horrors!

    So will the green bottles be politically correct while use of those clear bottles be taxed in compliance with the political “cap and trade” anti-carbon religious decree being promoted?

  15. Re Kyle

    Don’t worry too much about stuff leaching out. That may already have happened in the time between bottling and consumption of the original acid rich contents. It’s an interesting comparison of Western concerns, ie potential BPA contamination versus more pragmatic concerns over access to potable water which much of the world’s population doesn’t have. If this is really a way to provide safer drinking water, then it seems a far better use of our cast-off/recyled bottles. How do we get our bottles to those that could use them though?

  16. Curiousgeorge says:
    May 15, 2011 at 3:38 pm

    Have we now accepted our global pre-industrial fate? Have you resigned yourself to slow, cold, and dim? Are we to be conditioned to accept this kind of 3rd world poverty even here by WUWT? I expected better from you. A man 30 years my senior, once offered some good advice many years ago: “Live as well as possible for as long as possible”. I intend to do so.

    This kind of abject minimalism does not offer much hope of a brighter future.

    George, if this method is adapted widely, it will save the lives of millions of children. In my world, that is hardly “minimalism” to be disparaged …

    w.

  17. James Sexton says:
    May 15, 2011 at 4:10 pm

    I like the idea, but I’d still favor a cap full of Clorox/quart. I don’t have the effectiveness numbers handy, but is sufficed for the U.S. Army while I was in, so probably quite a bit more effective than the SODIS method, but I agree, you can’t beat the cost. If this is the only method available, it sure beats nothing.

    That would be my vote as well … but then a full bottle of Chlorox doesn’t represent say five days wages for me, as it does for far too many folks on the planet …

    w.

  18. Kyle Anders says:
    May 15, 2011 at 4:01 pm

    … I wouldn’t assume this is a good idea over the long term, and yeah, some studies might be in order. Although letting plastic bottles filled with water bake out in the sun for ours may be effective at decontaminating the water, you’re also introducing unintended consequences, namely creating ‘plastic tea’ through the release of numerous petrochemical compounds from the plastic that leach into the water much more readily under high temperatures. BPA is one example, with several others to be concerned about depending on the grade of plastic. Yes, in a life or death situation such concerns are foolish, however for long-term, practical solutions in developing countries, there are much healthier and humane ways of decontaminating drinking water than scorching it in plastic. Here is just one example: http://www.enviro-stewards.com/?page_id=155

    What you say is true, but only in theory. And when we get out of the “life-and-death” situation, those ideas may help … although I have grave doubts about the Enviro-Stewards proposal for “biofilters in Southern Sudan”, sounds like parachute aid to me.

    But for now, for many people it’s a choice of a) possible minimal effect from leached chemicals or b) probable sickness and death for the kids.

    Not too hard a choice where I come from … of course, in the long run clean piped water is the solution, whether biofiltered or industrially cleaned in some way. But for now, we have to have solutions for the world in which we find ourselves.

    w.

    * Parachute Aid— a term of art in the world of village level development. Refers to experts who “parachute” in a package of technologies, and the leave and then expect the technological stuff to continue working …

  19. How about a crude one meter diameter parabolic mirror made of aluminum foil and cardboard to bring water to a boil? It could work for cooking as well.

  20. Anthony Watts says:
    May 15, 2011 at 3:13 pm

    No, no, no Willis…this is all wrong.

    No, no, no Anthony…this is all wrong. There is no money to be made from it.

    And I live in a Third World country. By the way I don’t need to shake bottle and put it out in the sun. I drink directly from the tap. ;O)

  21. Richard S Courtney says:
    May 15, 2011 at 3:05 pm
    Willis:
    It is common practice in many hot countries.
    Richard

    Not in mine. This is new to me and I live in a hot country. I guess I should have used my common sense about UV. :O(

  22. Kyle Anders says:
    May 15, 2011 at 4:01 pm

    … I wouldn’t assume this is a good idea over the long term, and yeah, some studies might be in order. Although letting plastic bottles filled with water bake out in the sun for ours may be effective at decontaminating the water, you’re also introducing unintended consequences, namely creating ‘plastic tea’ through the release of numerous petrochemical compounds from the plastic that leach into the water much more readily under high temperatures. BPA is one example, with several others to be concerned about depending on the grade of plastic. Yes, in a life or death situation such concerns are foolish, however for long-term, practical solutions in developing countries, there are much healthier and humane ways of decontaminating drinking water than scorching it in plastic. Here is just one example: http://www.enviro-stewards.com/?page_id=155

    Is a glass bottle OK?

  23. Kyle Anders says:
    May 15, 2011 at 4:01 pm

    I have both glass and plastic bottles. You have a good point that is why I pointed out glass. The above solution by Willis is still valid.

  24. “Six hours in the sun and the oxygen plus the solar UV kills diarrhea.”

    Sorry but diarrhea is a result not a cause. Which bacteria/virus does this method kill? Is it effective on bacteria/virus that would cause problems other than diarrhea? What if the used water bottle mouth is contaminated? Perhaps one could also sterilize urine and really help reduce water consumption.

  25. Willis,
    I find that many people who have never ‘seen’ the world they tend to have a skewed view of things (TV, magazines, etsc). Many assume that most Africans are starving – this is not the case. Many assume that the Pacific island atolls are sinking – this is not the case. Your travels and experience are invaluable. Keep up the good work.

  26. Jimbo,

    I do believe that glass would not be as effective due to the UV absorptive/reflective nature of the silicon dioxide material. One does not sunburn in a auto with the windows up ;)

  27. 5 people watching someone place water bottles of undetermined origin, upon a rack to be sterilized by sunlight.
    While billions are spent to mitigate global warming.
    Does somebody have a guilty conscience ??
    Or is guilt the the driver, behind this newest of business plans.

  28. Willis Eschenbach says: May 15, 2011 at 4:35 pm
    . . .but then a full bottle of Chlorox doesn’t represent say five days wages for me, as it does for far too many folks on the planet . . .

    Clorox is a 6% solution of sodium hypochlorite and 90% advertising. Cheaper to buy a couple pounds of sodium hypochlorite and mix up your own.

  29. Willis said, “… but then a full bottle of Chlorox doesn’t represent say five days wages for me, as it does for far too many folks on the planet …”

    Not yet. I suspect that is BHO’s goal, though. At least, it appears to be his policy.

  30. At 3:20 pm, responding to Dr A, Dr. Leif provides a quote (no attribution) regarding bread and cake – and all-in-all makes a good point.

    The history of this quote or statement may not be known by readers, or more likely, know erroneously. Have a look:

    http://en.wikipedia.org/wiki/Let_them_eat_cake

    ~~~~~~~~~~~~~~~~~~~~~

    Another thought about clear versus clean water:
    Our water, from 64 feet down, comes with ‘reduced’ iron and sometimes other undesirable things. Getting the iron out involves interesting science and technology. After 22 years the first system failed and was replaced last year. During the re-install we added 4 filters under the sink in the kitchen and a new ‘drinking water’ tap. If the new equipment lasts for another 22 years I will be pleased.

    The clear plastic bottle “shake & shine” technology would likely also oxidize the iron and produce a drinkable but uninviting product and after two or three uses the bottle would gain an unsightly interior coating. Still, it sounds better than diarrhea. The photo for the post shows exceptionally clear water in plastic bottles. I wonder about that?

  31. Oh, oh! The bedwetter greenies will not like this idea as they all know that there will be lethal amounts of chemicals (even at kilograms per bottle!) leached from the plastic under these conditions. The drinkers of this polluted, deadly water will not have diarrhea but will become hungry human-eating zombies, not unlike the more devout vegetarian-carnivore tree-huggers. This is common knowledge to the alarmists. Imagine coming up with a good use for plastic bottles; it’s just not possible for something invented by free market capitalism to come up with anything good. ;-)

  32. The Abstract is a bit vague to me……

    At baseline 62.4% of the study households had stored water which met World Health Organization guidelines for zero thermotolerant coliforms per 100 mL. Dysentery was recorded using a pictorial diary. Incidence of dysentery was significantly associated with higher motivation, defined as 75% or better completion of diarrhea data. Incidence rates were lower in those drinking solar disinfected water (incidence rate ratio 0.64, 95% CI 0.39−1.0, P = 0.071) but not statistically significant. Compared with the control, participants with higher motivation achieved a significant reduction in dysentery (incidence rate ratio 0.36, 95% CI 0.16−0.81, P = 0.014). However, there was no significant reduction in risk at lower levels of motivation. Solar disinfection was not significantly associated with nondysentery diarrhea risk overall (P = 0.419). A statistically significant reduction in dysentery was achieved only in households with higher motivation, showing that motivation is a significant determinant for measurable health gains. Failure of three-quarters of participants to achieve a significant reduction in dysentery suggests that research into effective implementation is required.

    “Higher motivation” ? This may mean an awareness to promote better hand to mouth hygiene and this factor more than drinking water may have reduced dystentery in this group. But I would need a definition.

    Unfortunately the full text is behind a paywall.

  33. I reviewed some of the referenced literature at the SODIS site. As expected, disinfection of micro-organisms is easiest when they are “free-floating” or in their “vegetative” state. When micro-organisms protect themselves by forming spores or cysts, they can become very difficult to inactivate. Another concern is re-growth after disinfection, as the SODIS process does not provide for any bactericidal effect after treatment.

    Here are selected quotes:

    Boyle, et al. 2008:

    …bacterial species which are spore forming may survive

    Complete inactivation (i.e., reductions greater than 4 orders of magnitude (4 log units) and final population below the limit of detection, which is 17 CFU/ml) was achieved within 3 h of exposure to sunlight for all the species studied except B. subtilis endospores, which experienced a reduction of only approximately 0.5 log unit by the end of the first day’s exposure of eight consecutive hours. These B. subtilis samples were re-exposed on the following day. After a cumulative exposure time of 16 h of natural sunlight (Fig. 1b), the maximum reduction observed for the endospores of B. subtilis was 96.3% (standard error, 3.0%), which corresponds to a 1.3-log-unit reduction for a cumulative global received dose of 79.9 MJ m^-2. (CFU=Colony Forming Units) (parenthetical comment added)

    In light of the well-documented resistance of B. subtilis to heat and pressure sterilization (23), it is remarkable that SODIS was able to inactivate as much as ~96% of the B. subtilis endospores at all. These results are supported by the recent findings of Mendez-Hermida et al., whose SODIS studies of the highly resistant oocysts of the protozoan pathogen Cryptosporidium parvum showed that exposures over two consecutive days of strong sunshine were typically required for their complete inactivation …

    Gómez-Couso, et al. 2009:

    However, SODIS field trials in different geographical regions, carried out by SANDEC, have shown that temperatures above 45°C are rarely reached.

    A reduction in oocyst viability of approximately 50% points (from 91.60% to 40.70%) was detected in samples with a turbidity level of 0 NTU, whereas for highly turbid water samples (300 NTU) the reduction was very low (from 91.60% to 80.64%). (NTU=Nephelometric Turbidity Unit)(parenthetical comment added)

    Laboratory experiments have shown that in water samples of turbidity higher than 200 NTU, less than 1% of the total incident ultraviolet light (UV) penetrates further than a depth of 2 cm from the surface (Joyce et al. 1996). It is therefore recommended that water destined for treatment by SODIS do not display turbidity levels above 30 NTU (EAWAG 2008).

    …when the temperature of the water did not surpass 25°C, the decrease in the oocyst viability in water of 300 NTU was very low, independently of the time of exposure.

    …after SODIS procedures, some bacteria may regrow, and therefore the EAWAG recommends that SODIS treated water should be consumed within 24 h after the treatment (EAWAG 2008).

    Heaselgrave, et al. 2006:

    No SODIS-induced reduction in (Acanthamoeba) polyphaga cyst viability was observed for sample temperatures below 45°C. (parenthetical comment added)

    In conclusion, it would appear that SODIS can be a very effective disinfection method. However, turbidity removal prior to SODIS treatment is very important. More critical is the fact that SODIS is ineffective against amoebas, due to the fact that temperatures above 45°C are rarely reached (Boyle, et al. 2008) and that no SODIS-induced reduction in viability was observed below temperatures of 45°C (Gómez-Couse, et al. 2009). SODIS mentions this serious limitation by stating:

    Amoeba species (that cause) Amibiasis (are) (n)ot rendered inactive. Water temperature must be above 50 °C for at least 1h to render inactive!

    However, from McGuigan et al. 2005:

    Higher temperatures are usually only achieved if the reactor is fitted with either rear-foil reflectors or the rear surface is coated in a matt black substance (paint, mud, etc.).

    If clean food-grade bottles (such as used soft-drink bottles originally bottled by multi-nationals) were used as SODIS reactors, then concerns about chemicals leaching out into the water would already have been addressed by the multi-national corporations as they would generally have to meet first-world standards for all of their packaging. I would also submit that perfectionism is the enemy of improvement in this case. Indeed, the marginal risk of leaching of chemicals from plastic bottles, assuming that clean food-grade bottles are used, is so completely masked by the far greater risks of disease and chemical contamination already present in the source waters that it is essentially zero.

    In summary, SODIS would seem to have a very large benefit to cost ratio.

  34. I am quite sure polyethylene terephthalate bottles absorb the UV rays in that area of the spectrum or if a little can go through it is surely not enough to do the job. I would however give more credence to heat and the presence of oxygen. One other possibility for this observed action is that some chemicals could be leaching from the plastic material and those combined with oxygen and heat could be the source for sanitizing the water from harmful bacteria.

    One thing is certain, on the long run, the decomposition by-products of the plastic bottles will have a longer impact on their health. It might not be immediate as is the case for those bacteria giving diphtheria but it will certainly be more harmful and who knows what those chemicals will do to their genetics on the long run.

  35. Willis,

    In your Cold Equations you call Temperature a flow. But Temperature is a measure of Energy.

    1 eV = 11,605 deg K.

    You can look it up.

  36. Glass bottles break & can then no longer hold water. If Enviro-Stewarts really cared about the ends not the politics, they would provide plastic bottles that bounce not break. That can later be used for this method, or other useful things. Glass takes much more energy to make, transport and more resources.
    If you are going to give them something to filter water, instead of that whole complex bio-sands thing, why not Reverse osmosis run by human pumping or MSR Miniworks & give it to them. Then the best thing would be to help them build power plants, drill wells or harness other water sources & build treatment plants.

  37. Genghis,

    This method would not be nearly as safe as filtration. It wouldn’t get rid of giardia, cryptosporidium, ascaris eggs (a large roundworm that lives in the intestines in about 30% of the world’s population, over 90% in Africa alone). According to Katadyn’s specs it will filter down to 0.2 micron, good enough for just about all bacteria, but not common viruses that can cause diarrhea (rotovirus and norwalk). The sodis method seems to kill a large portion of the bacteria that can cause diarrhea.

  38. Speed says:
    May 15, 2011 at 3:56 pm

    “According to the World Health Organization, more than two million people per year die of water-borne diseases, and one billion people lack access to a source of improved drinking water. (Wikipedia).”

    And while people in third world countries die of disease, we give how many billions of dollars to the CAGW climate elites for “research”?

    This is a great example of our grossly misplaced priorities…

    Ray says:
    May 15, 2011 at 7:16 pm

    “One thing is certain, on the long run, the decomposition by-products of the plastic bottles will have a longer impact on their health. It might not be immediate as is the case for those bacteria giving diphtheria but it will certainly be more harmful and who knows what those chemicals will do to their genetics on the long run.”

    Spoken like a true elite who has plenty of clean water to drink…I’m sure the sick and dying poor people really care about your unsubstantiated claims about plastic bottles…

  39. Soil solarisation has been used by some horticulturalists for decades: cover damp soil with *clear* plastic sheet, and the heat and uv dispose of a high proportion of plant pathogens. I was involved with some research in this area, and it NEVER OCCURRED TO ME that it might work to disinfect water. Very humbling.

  40. This little company in Australia has developed a very low cost solar desalination plant that works extremely well (won the inventor of the year a few years ago – I believe that Rotary International is funding distribution into “developing” countries);

    http://www.fcubed.com.au/aspx/home.aspx

  41. Add a drop of iodine and you can probably get rid of that last 25% and do a great dietary service for populations with a low iodine diet where goiter is common.

  42. The good done by treating some bottles of water can be undone if untreated water is also consumed.
    In a paper in preview, an incidental analagous situation is here quoted ananymously in part until publication: “In 1853-54 there was a serious outbreak of cholera in London’s Soho district….. Had Dr Snow derived only the average number of cholera-related deaths in each street in Central London he would not have been able to challenge the orthodox view. Snow instead showed how the incidence of cholera in the 1854 outbreak was closely correlated with the nature of the drinking water supplied by the Southwark and Vauxhall water company on the one hand, and the Lambeth company on the other, to individual houses on the same streets.”
    So management as well as treatment of water is needed. The bottle idea is so simple that it is worth widespread trial, even if it saves fewer lives than anticipated. Nice find, Willis.
    BTW, opposition to water treatment by fluoridation (government compulsory interfering with rights of people) is easily answered if you ask if chlorination should be stopped for the same reason. This program should not be stopped for fear of plastic leachates, the good far outweighs the harm – same logic.

  43. Anthony.
    There is nothing new under the sun!
    In 1965 I left the UK to live in South Africa. I came across this same sterilization of dirty or suspect water then. The were using large empty clear glass wine bottles simply left out in the hot sunlight for a day or two. I realized at the time it wasn’t the temperature but probably the ultra violate that killed the bacterium, that lives in most water sources throughout Africa.
    I believe this was not taught to the Native population but rather discovered by accident from simply storing the water in any container that was free/available and handy, after I found the water taste and clarity improved dramatically.
    As for enough wine bottles there was and still is millions of them available. South Africa has always produced some of the best and cheapest wines under the sun and lots came in a one gallon bottles some of it was good drinkable domestic (dirt cheap) white wines from the Cape.
    On a last note I never witnessed people sterilizing water in plastic bottles. I believe it was because of the plastic taste of water heated in pop bottle or container. This memory has stuck with me for over 45 years as a survivalist idea for drinking water.

    REPLY: Note the author

  44. Frank K. says:
    May 15, 2011 at 8:34 pm

    I speak as a chemist.

    A minimum of research in this system could improve it and improve their chance for a better life.

  45. The old European method of water purification was to add some sugar from malted barley and yeast. If it didn’t stink, it was safe to drink.

  46. BPA – no worries. Those plastic water bottles start out as tiny miniatures which are then inflated to full size by highly pressurized super heated steam. I’m sure that any chemicals likely to leach out were consumed by those who would pay for bottled water when the safest water on the planet comes out of their kitchen taps for free. I find the notion that anything will leach out at +45C that didn’t leach out from super heated steam rather odd.

    Turbidity – yup, that’s a problem. Let the water sit in a pail until it settles, then pour the clear stuff into the bottles… rocket science this isn’t.

  47. It has been said that humanity can be divided into two basic groups: those that drunk bear and those that drunk tea. Or in other words, some societies sterilised their drinking water by brewing it and creating alcohol, others boiled the water.

    Perhaps this is a third group?

  48. Evian spelled backward is “naive”, ho, ho.

    Our ancestors’ way of killing the wee beasties in water was to mix a bit of alcohol with it . . . or make beer, ale or “short” beer, that is carbonate it. Making wine is very easy to do, and last I looked, completely legal for your own consumption. “Drink a little wine for thy stomach’s sake”. Before our highly sophisticated public purification of piped water, by adding a bit of chlorine to it, drinking plain ole water might well result in death.

  49. intrepid_wanders says:
    May 15, 2011 at 5:35 pm
    Jimbo,
    I do believe that glass would not be as effective due to the UV absorptive/reflective nature of the silicon dioxide material. One does not sunburn in a auto with the windows up ;)

    Back to plastic I suppose. ;)

    n India, already more than one quarter million people use the SODIS method to treat their drinking water. However, especially in India, reports on hazardous substances in PET bottles have caused uncertainty among users and prevent a rapid dissemination of the method. In particular the family of plasticisers has recently given rise to discussion. While no plasticisers are used in the manufacture of PET, traces of these substances have already been detected in mineral water from glass and PET bottles. In 2008, Empa, the Swiss Federal Laboratories for Materials Testing and Research examined the risks involved in the application of the SODIS method (Schmid et al 2008). A recent study by the Indian Institute of Technology in Chennai with PET bottles from India now confirms the results of the Empa study: during the SODIS process, only very small plasticiser quantities are released in the water, and the WHO limiting values for drinking water are never exceeded. Therefore, the SODIS method does not constitute a health risk if applied correctly – the people in India can safely continue to drink their SODIS water.

    http://www.sodis.ch/index_EN

  50. Better in the long run to supply these people with piped potable water to let them get on with their lives.

  51. Having lived a substantial part of my life in 3rd world countries – all I can say is this is brilliant. The water bottles are common where I lived, because the local untreated water can kill you (people pay almost any price to stay healthy). I got sick many times.
    I am still bemused living in my native Australia at the resistance of the politically correct to plastic water bottles.
    Brilliant, cheap and simple.

  52. crosspatch says: May 15, 2011 at 9:41 pm
    Add a drop of iodine and you can probably get rid of that last 25% and do a great dietary service for populations with a low iodine diet where goiter is common.

    Good comment

    Additionally letting the kids have and teaching that a bottle (and cup/spoon) belongs to them (property) and ONLY THEM serves to reduce x-infection that results in salmonella, shigella and cambylobacter etc.

    I am not sure what UV does to giardia, a dust born cyst resulting in 3-4 sloppy diarrhoeal motions/day. I recall that UV filtering may not have decreased giardia outbreaks in the Australian desert communities, but can not be sure that this is the case.

    Good post Willis.

    Geoff Sherrington http://wattsupwiththat.com/2011/05/15/sodis-roolz/#comment-661188
    Soho pump was pumping shitty water out of the Thames due a gross system where effluence mixed with the water for human consumption http://www.lavoisier.com.au/articles/climate-policy/garnaut/Curtin-the-science-of-climate-change-and-carbon-taxes.pdf (source Lavoisier Society)

    Fluoridation of the water supply decreases tooth decay, a major factor in heart disease and dental disease leading to other diseases of kids.

    Kids at school (they have survived 0-5 yr time-line for some reason) are more likely to be provided with sanitation, clean drinking water, nourishment, personal safety and THEIR OWN INDIVIDUAL PROPERTY (toothbrushes, mugs, pencils, privacy and clothes etc).

    Providing safe and drinkable water by such a simple technique is a useful enterprise as Willis points out.

  53. Jimbo:

    Thankyou for your comment to me at May 15, 2011 at 4:51 pm.

    I have seen the method being used in several African and South American countries but – as you say – that does not mean it is in use in every place where it could provide a benefit.

    I am grateful for your correction of my observation. As is always true for eveerybody, my personal anecdote is limited by my personal experience.

    Richard

  54. In conclusion, it would appear that SODIS can be a very effective disinfection method. However, turbidity removal prior to SODIS treatment is very important. More critical is the fact that SODIS is ineffective against amoebas, due to the fact that temperatures above 45°C are rarely reached (Boyle, et al. 2008) and that no SODIS-induced reduction in viability was observed below temperatures of 45°C (Gómez-Couse, et al. 2009). SODIS mentions this serious limitation by stating:

    Amoeba species (that cause) Amibiasis (are) (n)ot rendered inactive. Water temperature must be above 50 °C for at least 1h to render inactive!

    This temperature limit could be easily exceeded with a minor change in the solar exposure configuration. You would only need a small amount of concentration of the sun to reach that temperature.

    Any sort of trough reflector setup could easily double or triple the solar concentration on the bottles. Trough reflectors located so their optical axis is a few degrees below the suns local noon time altitude in tropical climates should reach those temperatures with no difficulty. The higher solar isolation at the bottles location in the apex of the trough would also shorten the exposure time necessary to achieve required UV exposure, and help compensate for days with high overcast conditions.

    A trough reflector concentrator is simply two reflective sheets placed to form an accute V shape with the central axis of the V pointed toward the noon day sun , with the long axis of the V oriented east to west. In that configuration the day time sun would be shining down the V and the solar isolation at the bottom of the V would be any where from 2x to 10x the day time noon sun intensity, depending on how large the plates are. Commonly trough reflectors are designed as parabolic reflector troughs but for this situation that would be the hard way to do it.

    Much easier to build from local materials would be a simple V trough reflector as in this image.

    Putting a top cover of a thin sheet of plastic over the bottles to help insulate them in an inclosed box would also help increase the stagnation temperature of the water.

  55. Interesting that the “Deniers” of this process 100% ignore the fact that it works and has minimal associated expense. Dredging up the null hypothesis: What if this process didn’t work at all? Then the consequences would be dead children and heart broken parents.

    This method is a beautiful example of going with an imperfect but working solution while waiting for an affordable perfect solution to be discovered. I have no doubt that blink charts of deaths caused by chronic exposure to diarrhea vs chronic exposure to leached chemicals will favor this solution. Given a choice I will take the plastic tea every time. Meanwhile, hopefully the hand wringing SODIS deniers are spending all their free time finding an equally useful and affordable solution.

  56. Thanks for bringing this up Willis, this will save many lives if it gets wider adoption and just a small amount of money to educate and set communities up with a cheap ‘starter kit’ of bottles/reflectors.

    However, I think this must only be used as a method of last resort, and in no way should it replace schemes designed to provide people with a piped supply of potable water.

  57. Don’t forget that plastic bottles are made to biodegrade much faster today than the older types.

    Although it is a simple and easy solution in times of survival, it should not be a long term solution.

    As I said, I really doubt that the UV rays are doing anything in the process since they are most likely absorb by the plastic. This could be easily verified and if true they could use glass bottles and reduce their intake of decomposition chemicals and heavy metals.

  58. I too think SODIS is a great idea and have made a donation on their web site to support their efforts. They can use all the help they can get. If you are making a donation they accept VISA and M/C and for VISA at least (I didn’t try using M/C) they use the Verified By VISA process which helps insure a safe payment gateway. When the payment says (the next page after selecting VISA) “Postfinance VISA” it is merely one of their Swiss banking system names for VISA.
    Arguing over if any possible BHP contamination as a risk is pointless when you consider the people this is intended to help – the poorest folks on our rich green earth! They would just like to live another day without they or their children falling ill to preventable disease. Let’s work on disseminating this information and assisting in making it the best process possible when the people have no other resources – no money for bleach or iodine as an example – but can use plastic bottles and very simple filters (leave filters in sun to sterilize). Spread the word!

  59. Hi Willis, we have been working with the SODIS idea since 2005 in collaboration with the Luxembourg ILFBV NGO in programs in Africa and South America. It works quite well. And working also on many other simple things for helping kids and the general population in Africa. See our website in French:

    http://www.mitosyfraudes.org/Francia/festival.html

    and http://www.mitosyfraudes.org/Francia/naguirre_artemisia.html

    Procédé SODIS de stérilisation de l’eau
    De l’eau contaminée par des bactéries, mise au soleil dans une bouteille en plastique pendant 6 heures devient complètement stérile.
    Notre ONG a déjà réalisé des projets pilote dans plusieurs pays : Colombie, Pérou, Malawi, Palestine, Maroc.

    ***************
    And Jimbo: Glass is not so good for SODIS because it filters UV radiation.

  60. @various commenters
    Don’t you realize that anything that solves a problem identified by Greens is anathema to Greens.

    Overall …… if the choice is between drinking water au naturel and using SODIS …… I know which I’d choose. You?

  61. I remember seeing an invention on the New Inventors (Australian ABC program) in which a chap had designed a plastic panel system with smallish cell-like structures designed to utilise sunlight to evaporate the water as it passed through by gravity. I can’t seem to find it ATM but I am sure I linked it at WUWT in another article some time ago.

    This solution is more practical as there is probably no shortage of plastic drinking bottles in less devevloped countries.

  62. I am sick and tired of being scolded for enjoying low-mineral water- the tap water in Mojave is typically 600 ppm total dissolved solids, and tastes like baking soda. I really don’t want kidney stones, either.

  63. A number of folks have commented that the SODIS method won’t kill everything. This is true. But if it can reduce the incidence of third-world childhood diarrhea in a given area by 80% or so, it is a huge win. Heck, if it reduces it by 10% we’re still talking lots and lots of kids.

    If things don’t get killed by the standard method, you just need to get the water hotter, which is easily done by a) putting it in a reflector (tin roof pieces, aluminium foil, pieces of tin cans, etc.), or b) half-way bury the bottle on its side in sawdust or hay or leaves etc. to slow heat loss, or c) throw a piece of clear plastic over a row of bottles on the roof and weight the edges to prevent air exchange, or d) all of the above, or e) some other cheap (preferably free) method.

    Me and a friend of mine made a preheater for water. We took a 100′ coil of 3/4″ black plastic pipe, plumbed it into the system before the water heater, and threw the coil up on the tin roof. We covered it with thin clear polyethylene sheeting, but in the summer we had to take the clear sheeting off … the water in the pipe was boiling at the peak of the solar day.

    These kind of things to me are perfect examples of the “no regrets” plan for dealing with the (likely imaginary) dangers of CO2. The “no regrets” plan is to do things that we will not regret doing even if CO2 is not the global thermostat. Let’s protect people now from the vicissitudes of climate. Then if climate does worsen we’re already ahead of the curve … and if it doesn’t, we’re even better off.

    w.

  64. As Ray above pointed out, plastic bottles blocks any disinfecting UV rays. Glass would be better, and not leach any chemicals into the water.

    Or is the idea that the heat alone is enough? I do remember from extended hiking trips that the old “boil for 5 minutes” meme is excessive. 60 degC will kill off most bacteria in the natural world, and you might get pretty close to that in a bottle on a tin sheet under the African sun.

  65. Everyone keeps making comments about if this or that is UV transparent.

    It very much depends on the specific item. For instance optical glass cut off of UV varies according to its refractive index with high refractive index glass tending to pass less UV than lower refractive index glass. Likewise common glass is more or less transparent to UV depending on the iron content of the glass among other things. Plastics also vary depending on thickness and if they are treated with UV resistant coatings.

    This doc shows the results of some testing. It implies that polyethylene has the highest UV transmission so perhaps in an emergency situation a common PE sandwich bag would the the container of choice, or a common PE milk jug.

    http://www.sodis.ch/methode/anwendung/factsheets/glass_pet_e.pdf

    In time, I know for a fact based on personal experience, that common PE milk jugs will get brittle after prolonged exposure to day time sun.

    Heat being the most reliable method, I see no reason that a continuous treatment system could not be developed for a central water supply, using a long length of appropriate tubing and a flow restricter to limit water movement to a drip by drip passage into a collection container.

    For a small village or even a family a few feet of tubing, an input container with sand filter, passing into the tubing which is coiled inside a heating chamber heated by a low concentration reflector then a drip restricter into a collection bottle could provide a near continuous supply of water which has been held at sterilization temperatures.

    You do not need to boil the water, the sterilization is a combination of temperature and residence time, with 165 deg F (74 deg C) sufficient to kill many common bacteria if held for 15 minutes or so. Higher temperatures allow shorter duration heat exposure (+80° C (176° F) for ten minutes or at +90° C (194° F) for one minute.

    Likewise UV sterilization is a combination of the intensity and duration. UV A being the preferred, but other high intensity light frequencies also can cause biological damage disinfection if duration or intensity is high enough.

    http://www.ncbi.nlm.nih.gov/pubmed/10169625

    I suspect that all of these mechanisms are at work in the real world.

    Larry

  66. Greens will pan this whole idea because it will save lives (they’ll have some other reason for it, rather than admit the truth). Their goal is to do something about what they consider a surplus population of six billion. So, they won’t be interested in this. Nothing to see, move along.

  67. Dan J says:
    May 16, 2011 at 2:24 pm

    As Ray above pointed out, plastic bottles blocks any disinfecting UV rays. Glass would be better, and not leach any chemicals into the water.

    No, Ray said that plastic might block UV rays, but I doubt that very much.

    w.

    [edited to add] I see DJ Hawkins beat me to it …

  68. Willis, you sure do generate interesting discussions.

    Some stray thoughts this discussion has sparked in my head:

    Plastic bottles have gotten much thinner. Glass can’t get so thin. I’ll bet the thinness of plastic allows more UV through.

    (Someone mentioned plastic bottles have been made more “biodegradable.” I wonder if “biodegradable” was some Mad Ave way of selling thinner bottles, and the word “biodregradable” is just a long way of saying “thin.”) (Very cynical of me, I know.)

    No one has mentioned how valuable a cheap microscope and a classroom would be, in rural Africa.

    As a small boy I used to drink water from places I shouldn’t have. I simply didn’t see any reason not to. Then I was told there were “germs” in the water, but remained slightly dubious, for elders also attempted to scare me into behaving by warning me that bogey men would get me if I misbehaved, and I knew bogey men were fictitious. It was only when I looked through a microscope and saw the “wigglers” in the water that I dropped my boyish skepticism, and became a believer.

    Education allows people to make the right choices on their own. I imagine an African boy, seeing “wigglers” through a microscope for the first time, would be every bit as excited and awed as I was. It was a revelation, and changed my behavior.

    Of course, a microscope is scientific, and seen-observations are reletively objective. When education moves into subjects involving morality, (IE: Liberal Arts,) it becomes more subjective, and prone to hypocrisy: In French Africa the French spent a century trying to “educate” African woman to wear tops, despite the heat. Just when the African women began to act educated, French women decided that going topless on the beach was the fashion, and if you didn’t do it you were a prude, and were uneducated. African women must have rolled their eyes.

    Climate Science seems to me, at times, a bit like Social Science, and thus not truely a science, but more like “Liberal Arts.”

    A posting like this, Willis, brings us back down to earth, and back to simple, basic science.

  69. Hotrod(LarryL) gives transmission of UV through plastics, glass. Thank you, I was about to do similar.
    Some have wrongly interpreted a previous post of mine. I’m all in favour of the idea as a wonderful low cost “no regrets” approach, but it does have to be scientifically supportable. The drop-off of intensity of UV approximately follows the Beer-Lambert law (for simple geometry). The water itself is also an absorber, so the thinner and the cleaner, the better.

    Having studied the effect of the introduction of tea to Europe, I arrive at the same conclusion as Peter Haydon in his book “An Inebriated History of Britain”. One review starts …
    “In 361 AD the Emperor Julian described the Teutonic northern European races as ‘sons of malt’. Big drinkers they all were, but none so much as the English. As this book shows, the English have spent much of the last 2000 years semi-permanently drunk”.
    That includes children. Sun-cleaned water sounds a better way.

  70. Thanks all above for the info on UV transparency. I had discounted this idea earlier on, but in this case I’m very happy to be proven wrong.

  71. Caleb http://wattsupwiththat.com/2011/05/15/sodis-roolz/#comment-661953 No one has mentioned how valuable a cheap microscope and a classroom would be, in rural Africa.

    Good comment.
    In Australia in the 70s microscopes were provided and local health workers in very remote areas were able to diagnose common diseases. And treat locally. Using a categorical box of medicines, similar to that provided by the Royal Flying Doctor Service (RFDS). http://www.flyingdoctor.org.au/About-Us/Our-History/ Source: http://www.flyingdoctor.org.au/

    We attempted the same, providing the same health workers 20 years later with proper instruments. But were called to task with a Territorial Ministerial that accused us of fraudulent use of training funds.

    Due to policies couhed as ‘self determination’ etc there was 20 years lost of primary and secondary education to these people, the children and grandchildren of these health workers. And now only city health workers (professionals) and career academics seem to hold the key for the regional/remote peoples. Wrong as it may seem.
    End of story.

    Doug Jones

    http://wattsupwiththat.com/2011/05/15/sodis-roolz/#comment-661690

    And one has to ask why the testing and results of local water sources is not available more publicly. And why testing parameters have changed.

  72. Apologies (Jessie)

    Due to policies couhed as ‘self determination’
    Should be ‘couched’.
    aka As express something in the language of a specific lifestyle.

    As in the lack of science utilised in premising, developing AND evaluating the policies, such as ‘self determination’ for eg.

  73. There is no reason to worry about BPA from the plastic. This is another alarmist scam originating from the BS section of a Master’s Thesis discussion section in which the student was BS’ing about why his results were what they were. Real world research has not found there to be a problem with BPA. This is another political/environmentalist boondoggle-screw-up, just like so many other issues.

    Also, they assume that the users of this strategy will apply it properly. Leave the water-filled bottles on the solar heater for several days and algae will grow quite nicely, which may not be all that nutritious or tasty.

    Years ago a do-gooder group tried to introduce formula bottle-feeding to Africa. They left the mothers with a supply of bottles and formula. The results were disastrous.

    First, bottle-feeding costs more than 4 times the cost of the food needed for breast-feeding, so the women could not afford more formula, that is if they knew to do so.

    Second, when the do-gooders returned a year later they found babies dying of malnutrition. They were being bottle-fed but the bottle contents were just water. The women thought that the nipples of the bottles had magical properties and did not know that the formula was the source of nutrition for the babies.

    The law of unintended consequences proven once again. In this case, it derives from ignorance of the do-gooders, not understanding or knowing the women very well

  74. Willis:

    If you wouldn’t mind I would like to correspond with you regarding this water purification issue.

    Would one of the moderators send Willis my email address?

    Larry

  75. S.E.Hendriksen says:
    May 17, 2011 at 3:10 pm

    The Moringa tree can do the trick in 0ne hour…. and with a lots of other benefits.

    http://www.treesforlife.org/our-work/our-initiatives/moringa

    Clarification through flocculation helps treat water, but in and of itself does not remove biological hazards although it “might” mechanically reduce the total counts the water although clear is still not necessarily safe to drink.

    It should be thought of as and adjunct pre-treatment to raw turbid water to help filtration systems remove the gross contamination, but I can see no mention that the flocculation treatment has any bactericidal action in this study, let alone viruses and other undesirable critters that cause disease.

    http://www.deutsch-aethiopischer-verein.de/Gate_Moringa.pdf

    This second study does show that it has some bactericidal properties but unlike broad spectrum sterilization by heat, UV, Ozone or Chlorine and Iodine, I think it is only a partial solution. It is also not clear if the flocculation process also accomplishes the bactericidal action or if it has to be carried out as a second step. Last in an environment where the country side is stripped of burnable trees to provide firewood it would be difficult to cultivate the tree as a crop unless you had significant local support for the project, where SODIS can be carried out by a single individual independent of the community attitude toward it.

    http://www.wef.org/WorkArea/linkit.aspx?LinkIdentifier=id&ItemID=5813

    I personally prefer a more broad spectrum solution like SODIS than a chemical treatment process that requires the locals to perform a process like flocculation which involves preparation of the seeds and the flocculation agent, then proper mixing and settling of the mixture.

    Larry

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